Symbol aided and pilot aided demodulation and its performance improvement using iterative decoding for fading channels

With equipping multiple antennas at both transmitter and receiver ends, the signals in the wireless OFDM systems could be transmitted over multipath fading channels for achieving benefits and high flexibility. In this paper, we focus on MIMO-OFDM systems that simultaneously perform channel estimation in order to combat additive noise, and multipath fading. The performance improvement is confirmed by simulations. Results show that the proposed MIMOOFDM scheme is quite robust in practical environments.

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Joint Angular and Time Diversity of Multi-Antenna CDMA Systems in Wireless Fading Channels

International Journal of Wireless Networks and Broadband Technologies ◽

10.4018/ijwnbt.2011010101 ◽

2011 ◽

Vol 1 (1) ◽

pp. 1-14

Author(s):

Feng She ◽

Hsiao Hwa Chen ◽

Hongyang Li

Keyword(s):

Fading Channels ◽

Performance Improvement ◽

Multipath Fading ◽

Antenna System ◽

Space Time ◽

Diversity Gain ◽

Multipath Fading Channel ◽

Time Diversity ◽

Time Domains ◽

Code Division Multiple

In this paper, a multi-antenna based receiver structure for direct sequence code division multiple access (DS/CDMA) system is proposed. The proposed scheme exploits the excellent time resolution of a CDMA RAKE receiver and uses an antenna array beamforming structure to resolve multipath returns in both angular and time domains. A much higher diversity gain than that based only on the time domain diversity can be achieved. This work suggests a new space-time diversity paradigm, namely angular-time diversity, which differs from traditional Alamouti-type space-time coded schemes. The impairments caused by multipath and multiuser interference are analyzed. The performance of the proposed receiver in multipath fading channel is explicitly evaluated. An expression for uncoded system bit error probability is derived. Simulation results show the performance improvement in terms of BER due to the use of multi-antenna in the receiver, and the results illustrate that the multi-antenna based receiver works effectively in resolving multipaths in both angular and time domains to achieve performance improvement due to angular and time diversity gain provided by the multi-antenna system.

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A Deterministic Construction for Jointly Designed Quasicyclic LDPC Coded-Relay Cooperation

Wireless Communications and Mobile Computing ◽

10.1155/2019/5249373 ◽

2019 ◽

Vol 2019 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Muhammad Asif ◽

Wuyang Zhou ◽

Qingping Yu ◽

Xingwang Li ◽

Nauman Ali Khan

Keyword(s):

Fading Channels ◽

Iterative Decoding ◽

Rayleigh Fading ◽

Additive White Gaussian Noise ◽

Ldpc Codes ◽

Destination Node ◽

Relay Nodes ◽

Binary Matrix ◽

Relay Cooperation ◽

Joint Iterative Decoding

This correspondence presents a jointly designed quasicyclic (QC) low-density parity-check (LDPC) coded-relay cooperation with joint-iterative decoding in the destination node. Firstly, a design-theoretic construction of QC-LDPC codes based on a combinatoric design approach known as optical orthogonal codes (OOC) is presented. Proposed OOC-based construction gives three classes of binary QC-LDPC codes with no length-4 cycles by utilizing some known ingredients including binary matrix dispersion of elements of finite field, incidence matrices, and circulant decomposition. Secondly, the proposed OOC-based construction gives an effective method to jointly design length-4 cycles free QC-LDPC codes for coded-relay cooperation, where sum-product algorithm- (SPA-) based joint-iterative decoding is used to decode the corrupted sequences coming from the source or relay nodes in different time frames over constituent Rayleigh fading channels. Based on the theoretical analysis and simulation results, proposed QC-LDPC coded-relay cooperations outperform their competitors under same conditions over the Rayleigh fading channel with additive white Gaussian noise.

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